Utilisation of traditional ecological plant classification systems to explain major dimensions of trait variation in herb layer of East Carpathians forests

Abstract

Among researchers, there is constant interest in using ecologically similar plant groups to analyse the principles of forest vegetation functioning. However, these groups are more often defined a priori with a certain dose of subjectivity and low repeatability. We expected, based on widely documented, categorical traits, that it is possible to distinguish a more objective, simple, universal plant group set for herb layer – an important component for temperate deciduous forest ecosystems’ functioning. These plant groups would reflect well the variation in key traits (economic, size and reproductive traits) which reflect the foremost dimensions of the ecological variation between herb species. Because this variation is interpreted as adaptation to the environmental conditions, we thus assumed its importance in understanding the principles of vegetation functioning in changing forest habitats. We proposed the plant group classification method based on categorical traits included in traditional ecological plant classification systems. We established that categorical trait-based plant groups align well with key trait-based classified groups of species. Moreover, categorical trait-based plant groups had high explanatory power for variation in key traits. We found that categorical trait-based plant groups align well with two main global axes of trait variation connected with economic and size related traits. Because the proposed categorical traits are very simple to access and available for most plant species, our results indicate that categorical trait-based plant groups may be widely used to explain the principles of forest vegetation functioning, especially in monitoring and explaining changes in vegetation.